An optical lens made of transparent resin is characterized by being lightweight, less likely to break, and easy to mold as compared to an optical lens made of inorganic glass, and is thus widely used in a variety of optical equipment. Thermoplastic resins such as polymethyl methacrylate, polycarbonate, cyclic polyolefin are known as transparent resins used for molding an optical lens.
These resin-molded products, however, have insufficient light resistance and heat resistance, and are discolored, age, and the like due to light irradiation. Further, a molded body made of polymethyl methacrylate or polycarbonate has low scratch resistance, and an optical lens made thereof has an insufficient surface hardness and requires a surface protective layer.
Transparent polyamides disclosed in Patent Document 1, Patent Document 2, Patent Document 3, and the like are also available for forming an optical lens. Patent Document 4 proposes, as an optical lens having a high surface hardness, an uncoated lens made of colorless, transparent copolymerized polyamides including a) at least one cycloaliphatic diamine having a carbon number from 6 to 24, b) at least one aromatic dicarboxylic acid having a carbon number from 8 to 16 in a nearly equimolar ratio, and c) up to 20 mol-% of polyamide-forming monomers.    Patent Document 1: Japanese Patent Laying-Open No. 62-121726    Patent Document 2: Japanese Patent Laying-Open No. 63-170418    Patent Document 3: Japanese Patent Laying-Open No. 2004-256812    Patent Document 4: Japanese Patent Laying-Open No. 9-137057